Differential gear



June 16, 1931-. G, H, BENZON, JR '1,810,747

DIFFERENTIAL GEAR Filed sept. 14, 192e lliqaltented AJune '16, 1931 enonsnjinisnnzoiv, Jn., or` JENKINTOWN, rnNnsYIivAnIA, Assreivon rro wIIIgIAM i sELLnnsacoivrrenmrnconronarnn, or rrIIIlAnnnrHIa, IEmsrLvANIaA roJaATIoN F PENNSYLVANIA DIFFERENTIAILGE'AR Application measeptemter 14, 192e.I serial'No. 306,023,`V 1

- This invention relates to improvements in; k'Ihe shafts 'aremounted `bearf f suited as hereinafter set forth for use in bora ing mills, lathes, and like machines employ-1k differential gears,y and has'for its principal object the provision of a novel differential geanhaving'the material advantagesiof extreme simplicity, relatively low cost of manu facture, and relatively high efficiency as com pared with gears similar purpose. v

Anotherobject of the invention is to provide a dierential gear particularly `well ing double-pinion drives for the moving carriages, although the utilityof the gear is not restricted to such machines and may be found useful in connection with any machine. re

quiring a limited differential. Y

In the attached drawings:

Figure l is a transverse sectional view ofy a differential mechanism made in accordance with `the present invention, as applied to the Acarriage traverse mechanism of a boring drilling machine;

Fig. 2 is a plan view of the parts shown in Fig..1, and

Fig. 3 is a diagrammatic view illustrating another application of my invention.

With Vreference to the drawings, the devicey comprises a pair of helical gears 1` and 2, right and left hand respectively, which are independently rotatable, being attached'respectively in the present instance to aligned yshafts 3 and 1. Meshing respectively Awith the gears 1 andy 2 vare pinions 5 and 6, these pinions being fixed with respect to each other and constituting in effect a single double helical or herringbone pinion. This pinion 5-6 is fixed in the present instance to a shaft 7 journaled in bearings 8 and being capable of limited axial movement therein. In the present instance, the shaft 7 carries at one end a spur gear 9 which meshes with a pinion l0 on a stub shaft 11 mounted in bearings 12, and this stub shaft 11 carries at its opposite end a spur gear 13 which meshes with a pinion 14 on the armature shaft 15 of an Velectric motor 16, the latter constituting the s ourceof power by which the gearsy 1 and 2 are driven through the intervening train of gearsincluding the pinion -e.V

previously employed for ings 17 ,and each oftheshafts carriesat its outerV end la bevel `'pinion 18.7 Each Vof the pin'ions-IS meshes with. a bevel gear 19Qcarlried at the upperend ofav4 `vertical shaft'20, 55

these `shaftsbeing j ournaled in bearings 21, 22 and having at. theirlowerl ends pinions 23 which operate in racks 211.2" Inthe present instancathe afo'refde'scribed mechanism, with the :exceptionof the racks24, is mountedvon a' 60 carriage 25 which isadjustablelon a base 26 to which the racks 21 are attached, `thecar-` riage being advanced or'retracted onj the base in obvious manner.`

In machines of this general character, inv 35 order to drive the carriage with truel recti linear movementfand withouty twisting on' the base, it .-is necessary toy provide means forv offsetting the small irregularities in the two'sets of gears and racks, andit is the function: of 70 the diEerential mechanism, including the gears 1 andi'2 andtheaxially movable pinion 5, -6, to f compensate forj these irregularities. It l will' be 5 apparentl that any change in the relative positions ofthe teeth'ofthe two racks 75 24 will destroy thebalanceof forces between thesegears land 2 andthe pinion 5-6,andwill" result in vran axial movement ofk thejpirif ionv which will tend continuously to" assume a position in which the pressures on theteeth 80 of the two gears 1 andf2 arefequal. 'A slight differencein the'v pitch of the immediately as? sociated rack whichV would cause the gearl 2, forexample, to `move somewhat-faster than the gearl willresultinan axialmov'eme'nt S5 ofthe pin-ionL 5%6 sufficient to maintain contact equally'on the'teeth of the'gears 1 and 2. An .opposite Arelative.act'ionof the gears 1 and 2 obviously-wouldproduce a reaction in the oppositedire'ction, ,andthe amount of axial 90 movement providedfor the pinion 5;(5 is in this case determined 'by the amount of variation .ini the ,teeth ofthe racks and 'gears.' r`irnother usefulapplication /of my invenf tion is `tocvertical boring` mills, in which ma'- 95 shinesy the strength and smoothness of action ofthe table gear are primeessentials.' V'Ioafford'greater strength with a given vlpitch and facegear aswell as increased smoothness of action, two driving'pinions meshing with the 100 one table gear or rack may be employed, as shown diagrammatically in Fig. 3, and it is preferable to set the pinions so that one of the teeth of one of the pinions is just leaving.

23a similarly indicate the drive pinions,which itwill be understood correspond to the pinions 23, 23 of the mechanism yshown in Figs. 1 and 2 and previously described, this dierential mechanism remaining the same.

The dierential mechanism within its operative limits has material advantages of simpl'icity and relative eiiiciency over the forms ofdiierential gearing commonly used in the L prior practice. While particularly suited for vuse in connection with the drives of certain. types of machine tools, other useful ap plications will be apparent, andthere is to be no limitation in this respect.

I claim:

l. A di'fferential mechanism comprising independentrright and left helical gears, and a double helical gear coactive with said iirstnamed gears and free to move axially within predetermined limits.

2. In a die'rential mechanism, the combi nation Y with independent drive shafts, of' rightY and left helical' gears mounted respectively on said' shafts; a second pair of gears meshingtherewith, said second gears being relatively fixed and axially movable Within predetermined limits; and a source of power operatively lconnected with said last-named gears. Y

3. The combination with a movable carriage, of drivingmeans therefor including a pair of drive pinions, a motor for driving said pinions, and power transmission means connecting the motor with the pinions and including a differential mechanism consisting of two helical gears right and left-hand respectively and respectively connected with said K pinions, and a double helical pinion meshing with both of said helical gears and axially movable within predetermined limits.

v4. The combination with relatively movable structures, of toothed means fixed to one of said structures, a pairiof drive pinions meshing with said toothed means, a motor for driving said pinions, and power transmission means connecting the motor with the pinions and including a diiierential mechanism consisting of two helical gearsright and lefthand respectively and respectively connected with lsaid; pinions, and a double helical pinr 1sV the table gea-r or rack represented by its pitch circle, and 23a,

ion meshing with both of said helical gears and axially movable within predetermined limits.

5. The combination with a movable carriage, of rack and pinion driving means for said carriage including a pair of drive pinions, a motor for driving said pinions, and power transmission means connecting the motor with the pinions and including a differential mechanism between the latter.

6. In combination, a. movable carriage, a stationary support therefor, a motor, two driving means connecting the carriage and support andl each including a rotatable element, and driving connections between the motor and saidv rotatable elements including a dierential mechanism arranged between the latter.

GEORGE H. BENZON, JR.

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